Penguins and Seals Create Invertebrate Hotspots On Antarctica...With Poop

In Antarctica, researchers have found areas rich with moss, lichen, and small-scale life, sustained in large part by elephant seal and penguin droppings.

Stef Bokhorst, an ecologist at Vrije Universiteit Amsterdam and lead author of the study that appears in Current Biology, says the biological hotspots are generally centered around "one big mass of penguin poop, or a big clump of elephant seals wallowing in their feces."

Penguins and seals feed on krill, fish and squid from the ocean. They come on land to roost and breed. "Their poo gets deposited on land and evaporates as ammonia, and then gets blown inland," Bokhorst says, creating a "nitrogen footprint" up to 240 times the size of the colony, an area of fertilized soil that supports a thriving community of mosses, lichens, bugs, and mites.

Bokhorst says the bioabundance surrounding the seal and penguin colonies-- millions of bugs and mites per square meter--far exceeds the ratio in US and European grasslands. It's a difference one can only see through a microscope, however. He spent months and months poring over samples he collected in Antarctica to quantify the abundance.

"Now we can predict where biodiversity hotspots are, and where our losses are, based on the presence of penguin colonies and how many penguins there are in that colony," says Bokhurst. He says they can be estimated through satellite imagery.

"The idea that that penguins and seals are responsible for bringing marine resources up onto terrestrial areas is very cool," says Heather Lynch, an Antarctic penguin ecologist at Stony Brook University. "We tend to think of marine and terrestrial as being separate ecosystems," she says, but this research shows that penguins and seals act as an "ocean to terrestrial conveyor belt," bringing nutrients from the ocean onto land through their natural behavior.

According to Bokhorst, most of the research on Antarctic biology has focused on cold temperatures and water scarcity, as limiting factors for supporting life. "The hypothesis [has been that] if you warm the place and get more water availability, things should grow better," he says. "But after 15 years of actual warming," not much has changed with the vegetation.

Bokhorst's research brings a third leg--nutrient availability--into the picture. Nitrogen availability is scarce in Antarctica, so penguin and seal excrement contributes significantly to the ecosystem. He expects these hotspots to follow penguins and seals, as they migrate in response to fishing pressures and shifting sea ice.

"The loss of a large penguin colony on the Antarctic Peninsula would have important effects," says Lynch. Penguins face changing environmental conditions on sea and on land. The move or loss of a penguin colony would generate ripple effects throughout the ecosystem.

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